Spontaneous Metabolic Regression in High-Burden Follicular Lymphoma: A Case Report.

Follicular lymphoma (FL) is an indolent but incurable B-cell malignancy, typically requiring therapy in patients with high tumor burden. Although spontaneous regression has been described, its frequency and durability are uncertain and require longitudinal follow-up. We report a 64-year-old man with high-burden FL fulfilling GELF criteria who deferred treatment and subsequently demonstrated a marked spontaneous metabolic response on a follow-up [18F]FDG PET/CT over a 6-month follow-up period. The metabolic response encompassed nodal, splenic, and serosal involvement, accompanied by resolution of symptoms and improvement in laboratory parameters. This case highlights the biological heterogeneity of FL and emphasizes the importance of individualized management and ongoing surveillance.